Heating of interstellar gas by galactic ultraviolet radiation

The process of heating interstellar gas by galactic ultraviolet radiation is investigated. The photoeffect on dust particles caused by ultraviolet radiation can act as a source of gas heating. The expression for gas heating rate is obtained. The characteristic features of the equation of a photoheated gas state and thermal balance in the interstellar gas are considered. While taking account of galactic ultraviolet radiation at the wavelength over 912 A, it is shown to be possible to build a two-phase model of interstellar gas with low values for the primary ionization rate by cosmic rays equal to 10-18-10-17 s-1. Photoheating decreases the temperature of the interstellar gas, and in some cases destroyes the two-phase structure